Cannot Save Multiple Objects To DynamoDB?

Question

I'm attempting to add multiple entries to my DynamoDB database through a service, but when the code is executed, Only one entry is saved. This is what I have done so far:

public int onStartCommand(Intent intent, int flags, int startId) {

    CognitoCachingCredentialsProvider credentialsProvider = new CognitoCachingCredentialsProvider(
            getApplicationContext(), // Context
            "us-east-1:851c121e-326d-4c9e-be47-fec40eb7b693", // Identity Pool ID
            Regions.US_EAST_1 // Region
    );

    AmazonDynamoDB client = new AmazonDynamoDBClient(credentialsProvider);

    Toast.makeText(this, "Adding To Database...", Toast.LENGTH_LONG).show();

    CognitoCachingCredentialsProvider cognitoProvider = new CognitoCachingCredentialsProvider(
            getApplicationContext(), // Context
            "us-east-1:851c121e-326d-4c9e-be47-fec40eb7b693", // Identity Pool ID
            Regions.US_EAST_1 // Region
    );

    AmazonDynamoDBClient ddbClient = new AmazonDynamoDBClient(cognitoProvider);

    DynamoDBMapper mapper = new DynamoDBMapper(ddbClient);

    String streamName = intent.getStringExtra("streamName");
    String userCreated = intent.getStringExtra("userCreated");
    ArrayList<String> selectedFriend = intent.getStringArrayListExtra("userInvolved");
    intent.getStringExtra("comment");

    for(int i = 0; i < selectedFriend.size(); i++){

        Streams streams = new Streams();

        streams.setStreamname(streamName);
        streams.setUsercreated(userCreated);
        streams.setUserinvolved(selectedFriend.get(i));
        streams.setUnread(true);
        streams.setDeleted(false);

        mapper.save(streams);

    }
}

And like i said, only one entry will be saved. I was suggested to use an arraylist, but I'm not sure how to go about doing that. Can anyone help?

All help is appreciated.

EDIT: The Streams.java class:

@DynamoDBTable(tableName = "Streams")
public class Streams{

    private String streamname;
    private String usercreated;
    private String userinvolved;
    private boolean unread;
    private boolean deleted;

    @DynamoDBAttribute(attributeName = "Stream_Name")
    public String getStreamname() {
        return streamname;
    }

    public void setStreamname(String streamname) {
        this.streamname = streamname;
    }

    @DynamoDBHashKey(attributeName = "User_Created")
    public String getUsercreated() {
        return usercreated;
    }

    public void setUsercreated(String usercreated) {
        this.usercreated = usercreated;
    }

    @DynamoDBAttribute(attributeName = "User_Involved")
    public String getUserinvolved() {
        return userinvolved;
    }

    public void setUserinvolved(String userinvolved) {
        this.userinvolved = userinvolved;
    }

    @DynamoDBAttribute(attributeName = "Unread")
    public boolean isUnread() {
        return unread;
    }

    public void setUnread(boolean unread) {
        this.unread = unread;
    }

    @DynamoDBAttribute(attributeName = "Deleted")
    public boolean isDeleted() {
        return deleted;
    }

    public void setDeleted(boolean deleted) {
        this.deleted = deleted;
    }
}

Answer 1

It seems your DynamoDB hash key is the user created field in the Stream class. This is the DynamoDB primary key which uniquely identifies a single item in the DynamoDB table.

Each time you call mapper.save(streams), you are overwriting the item you wrote in the previous iteration of the loop since it seems you only set the user created field once here:

String userCreated = intent.getStringExtra("userCreated");.

Try using a unique identifier (e.g. stream name as the hash key). If multiple items have the same hash key you can also use a schema with a range key to create a (hash key, range key) primary key to uniquely identify an item in the DynamoDB table.

Answer 2

DynamodbMapper has a batch save method that allows you to save multiple objects in a batch. Check out the DynamoDBMapper.batchSave.